Electric discharge tube or the like



SePt- 15, 1936 W. l.. KRAHL 2,054,221

ELECTRIC DISCHARGE TUBE OR THE LIKE Filed Aug. 2l, 1934 ATTORNEYPatented Sept. 1.5, 1936 l s UNITEDy STATI-.ash

PATENT OFFICE I to Hygrade Sylvania Corporation,

Salem,

Mass., a corporation of Massachusetts Application August 21, 1934,Serial No. 740,742 5 claims. (o1. 25o-27.5)

This invention relates to electric discharge tubes and more particularlyto such tubes as are used in wave repeating systems or the like.

Anobject of the invention relates to an im- 5 proved form of waverepeating device.

Another object relates to an electron discharge tube having an improvedform of electrode spacer.

A further object is to provide an improved rectier tube.

l A feature of the invention relates to a novel formof electrostaticshield for radio tubes or the like.

Another feature relates to a special form of insulator spacer member forradio tubes which is l treated in such a way as to cause it to act as anelectrostatic shield.

A further feature relates to a tube of the socalled shield-grid typewherein part of the electrostatic shielding means also serves as anelectrode spacing means, and wherein the electrostatic capacity betweenanode and control grid is reduced to a minimum.

A'still further feature relates to the novel organization, arrangementand relative location of g5 parts which go to make up a relativelysimple and economically manufactured radio tube.

Other features and advantages not specically enumerated will be apparentafter a consideration of the following detailed descriptions and theappended claims: i

While the invention will be disclosed herein as embodied inone knowntype and structure of electron discharge tube, it will be understoodthat this is done merely for purposes of explaining the invention andnot by way of. limitation. Accordingly in the drawing:

Fig. 1 is a partial sectional view of a tube embodying features of theinvention. l

Fig. 2 is a detailed plan viewof one of the composite shield-spacerelements according to the invention.

Fig. 3 is a partial view showing the invention embodied in the mount ofa full wave rectifier tube or the like.

Fig. 4 is a top plan view of the mount of Fig. 3.

Referring more particularly to Fig. 1, the numeral I represents indotted outline the enclosing envelope of any well known form ofelectrondischarge tube. While the drawing shows an envelopeprovided witha dome portion 2 and a metallic contactor cap 3, it will be understoodthat any other shape of envelope may be employed Merely for purposes ofexplanation, it will be assumed that the envelope I is provided with are-entrant stem 4, terminating in a press 5 wherein are sealed thevarious electrode lead-in or support wires 6 to I4 inclusive. Wires 6and I4 extend through a pair of spaced discs I5, I6, one of these discsbeing shown in plan view in Fig, 2. In accordance with the presentinvention, 5 each of the discs I5 and I6 consists of a sheet ofinsulating material such as mica or the like provided with a coating ofsuitable metal or conducting material such as carbon, graphite or thelike. This coating may be applied in any well known l0 manner bydipping, brushing, painting, plating, or spraying for example by theSchoop process. If desired the surface of the insulator discs may beroughened or otherwise treated prior to applying the metallic coating soas to prevent the l5 coating from chipping or peeling. As shown in Fig.2 the median portion of each composite disc is provided with a series ofperforations I'I to 21 inclusive and through certain of theseperforations are adapted to pass the corresponding wires 20 6 to I4inclusive. In order that the various wires and electrodes may beinsulated from one another, the median portion of each disc containingthe perforations I8 to 26 is left uncoated. It will be understood ofcourse that the disc may be 25 coated either on one side or on bothsides. In the latter case both faces of the disc containing theperforations I8 to 26 should be left uncoated. The perforation 22 isadapted to receive and support the cylindrical indirectly heated cathode28, 30 the metal sleeve of which is electrically connected to the wire 9as shown in Fig. l. The cathode may be heated by any well-knownheaterthe termin nals of which are connected to the wires I0 and I I.Surrounding the cathode 28 is a suitable con- 35 trol or signal grid 29in thev form of a wire wound helically around the supporting posts 30,3I The post 3I is connected by means of the conductor 32 to the metalcap 3. In like .manner surrounding the control grid is a shield-grid 33which may be 40 in the form of a wire helically wound around the posts34, 35, the latterpost being welded or otherwise fastened to the supportwire I2. Similarly, surrounding the control grid and shield-grid is asuppressor grid 36 which may consist of a wire 45 wound helically aroundthe posts 31, 38, post 31 being welded or otherwise fastened to thelead-in wire 8. Surrounding the suppressor grid is a hollow metal plateor anode 39 which is supported on the posts 40, 4 I, these latter postsin turn being 50 welded or otherwise fastened to the wires 1 and I 3.Surrounding the anode is a Wire mesh shielding electrode 42 which isfastened to posts 6 and I4.-

'I'he electrodes 33 and 42 constitute respectively 55 an inner andanouter shield for the electrodes '3 and 39. Likewise the compositediscs i5 and i6 at opposite ends `of the electrode assembly act tosubstantially close 0E electrostatically, the open ends of the variouselectrodes, thus in effect providing a substantially completeelectrostatic shield or cage between the control grid 29 and the anode39. The metallic coatings of the discs may be electrically connected tothe inner shield grid 33 and to the outer shield grid 42 in any suitablemanner. Preferably however, the posts S and i4 which carry the outershield grid pass through the coated areas of the discs as will be clearfrom the drawing, and if desired the perforations through which theseposts pass may contain metallic eyelets which may be welded or otherwisefastened to the said posts 6 and i4. A metallic strap may then beprovided between the post iii and thel post 35.

While the drawing shows one specific manner of mounting the compositeshield-spacer discs i5 and i6 with respect to the ends of theelectrodes, it is understood that this is merely illustrative and thatany other suitable manner of mounting may be employed as long as thesaid discs substantially complete the shielding between the control gridand the anode. If desired, the upper disc 1 6 may be made of sufficientdiameter so as to contact with the inner wall of the dome portion 2 tosteady the electrode assembly at its upper end. While the drawing showsthe discs i5 and I6 spaced from the upper and lower edges of theelectrode 42, it will be understood of course that the said electrode 42may be extended in length so that its lower and upper edges engagerespectively the metallic coatings on the discs l5 and I6 thuscompletely enclosing the anode.

Referring to Fig. 3 there is shown a mount for a full Wave rectifiertube comprising a press 43 into which are sealed the lead-in and supportwires 44 to 5| inclusive. Mounted on the wires 41 and 48 is a compositedisc 52 consisting of a sheet of mica or similar insulating materialhaving coatings of metal suitably deposited or applied to opposite facesof the disc. Preferably, although not necessarily, the metallic coatingson opposite faces of the disc 52 are smaller in area than the discitself so that there vis an uncoated area around each edge of the disc.The wire 41 contacts electrically with the coating on one-side of thedisc while the wire 48 contacts with ing on the opposite side of thesaid disc. Mounted in spaced relation to one side of the disc 52 is asuitable electron-emitting cathode 53 which, merely for purposes ofexplanation, is shown as an indirectly heated cathode provided withheater filament terminals connected to the wires 45 and 46 and with atubular metal cathode sleeve 54 connected to the 'wire 44. A similarcathode 55 the coatis mounted in spaced relation to the opposite face ofthe disc 52. It will be understood that any well known means may beprovided for maintainingthe cathodes 53 and 55 in their predeterminedspaced relations with respect to the metallic coating 55 and themetallic coating 51 on disc 52. The coatings 56 and 51 therefore serveas anodes to the cathodes 53 and 55 and the insulator por- 'tion of thecomposite disc effectively insulates the two metal coatings from eachother and also shields the cathodes from each other. Since the metalliccoatings 56 and 51 are required to act as anodes, preferably althoughnot necessarily, they are constituted of a metal such as iron, nickel orthe like which is not materially affected by the heat or bombardmentfrom the cathode.

Various changes and modifications may be made herein without departingfrom the spirit and scope of the invention. f

What I claim is:

1. An electric discharge tube having a pairof electrodes, anl insulatormember interposed between said electrodes, and a metallic coating on thesurface of said member except at the regions where said member connectswith'said electrodes.

2. A tube mount comprising a press supporting a plurality of pairs ofmetal uprights, an electrode supported on each pair of uprights, aninsulator member through which said uprights pass to insulatingly keepsaid electrodes apart, and a coating of metal on the surface of saidmember to serve as an electrostatic shield, said coating beingfore-shortened with respect toV one pair of uprights.

3. A -shielding cage for radio tubes or the like comprising a hollowcylindrical metal member'and f a pair of insulator discs closing off theends of said member, said discs being provided with localizedc'onductive coatings on-their surfaces and also being provided withperforations said-coating being fore-shortened with respect to certainof said perforations. A Y

4. An electric discharge tube comprising a pair of insulator discs, anelectrode assembly mounted between said discs, each of 'saiddiscs beingprovided with a conductive coating on its surface but with the medianportions of the disc surface uncoated, projections from certain of saidelectrodes engaging the uncoated portions of said discs, and projectionsfrom another of said electrodes engaging the coated portions of saiddisc.

5'. A composite shielding and spacing member for radio tubes comprisinga disc of insulating material having a conductive coating on the surfacethereof, said disc being provided with perforations to receive electrodeprojections, the portions of said disc surface adjacent'the perforationsbeing uncoated.

WALTER LOUIS KRAHL.

